Ultra-high-accuracy optical testing: creating diffraction-limited short-wavelength optical systems

1
Ultra-high-accuracy optical testing creating
diffraction-limited short-wavelength optical
systems
Kenneth A. Goldberg
2
Ultra-high-accuracy optical testing creating
diffraction-limited short-wavelength optical
systems
Kenneth A. Goldberg Patrick Naulleau, Senajith
Rekawa, Paul Denham, J. Alexander Liddle, Keith
Jackson, Erik Anderson, K. Bradley, R. Delano, B.
Gunion, B. Harteneck, B. Hoef,G. Jones, C. D.
Kemp, D. Olynick, R. Oort, F. Salmassi, R.
Tackaberry Center for X-Ray Optics,Lawrence
Berkeley National Laboratory in collaboration
with J. Taylor, G. Sommargren, H. Chapman, D.
Phillion, K. Dean, et al. M. Johnson, A. Barty,
R. Soufli, S. Bajt,et al. International
Lawrence Livermore National Laboratory
Sematech and the EUV LLC and VNL
KAGoldberg_at_lbl.gov, SPIE 2005, 5900-16
3
Consider two state-of-the-art telescopes
SDO Solar Dynamics Observatory
AIA
Normal-incidence mirrors Angular Resolution
0.6per pixel
Please see Soufli, et al. SPIE 5901-24 (Mon) SDO
/ AIA material courtesy of LMSAL
CHANDRA X-Ray Observatory
Nested glancing-incidence mirrors Angular
Resolution 0.5in 0.510 keV
NASA / CXC / SAO
4
Better optics / Better angular resolution is
possible
Resolution is set by design compromises
Telescope size  Detector-pixel
size  Fabrication limits  Collection
efficiency  etc. However, thanks to the
semiconductor industry,technology for much
higher quality lenses is now available in the
EUV. So, what does the semiconductor industry
want with EUV lenses?
5
Lithography follows Moores Law
DRAM half-pitch
Intel plans
industry plans
DRAM

45 nm 32 nm 22 nm 15 nm
2007 2009 2011 2013
2010 2013 2016 2019
8.6 GB 34 GB 69 GB
EUV
By 200913, mass production of lithographic-qualit
y EUV lenses.
6
Diffraction-limited EUV optics for
photolithography
EUV projection lenses may be thehighest quality
optical systemsever produced ? 13 nm, 90
eV Mo/Si multilayer-coated fornear-normal
incidence R 70(Lawrence Livermore, Lawrence
Berkeley, et al.) Diffraction-limited spatial
resolution Up to 0.3 NA, ƒ/1.67 Rayleigh
resolution 1.22 ? / NA ? 27-nm half-pitch
MET projection lens Courtesy J. Taylor, LLNL
7
Industry-funded EUV projection lithography
researchat Berkeley, Livermore, Sandia Natl Labs
patterned reflective mask
resist-coated wafer
Engineering Test Stand Sandia National Labs.
Courtesy, Bill Replogle
8
Reaching diffraction-limited performance
If you can measure it, you can make it.
Ultra-high-accuracy optical testing is the key ?
Visible-light and EUV interferometry with sub-Å
RMS accuracy.
9
Inaccurate interferometry cost NASA Billions
Before
Before
Hubble Space Telescope
Kenneth Goldberg, KAGoldberg_at_lbl.gov, SPIE 2005,
590016
10
Comparison of slope and roughness requirements
SDO  AIA instrument
EUV Lithographic Optics
Goal 32-nm half-pitch Slope error 0.31.0
µrad37-Zernikes measured MSFR 12 Åmid
spatial-freq. HSFR 12 Åhigh spatial-freq.
Goal 0.5 arcsec Slope error 5 µradfull
aperture Roughness 4.4 Å1/ƒ (4 µm, 4
mm) Micro-roughness 4.4 Å1/ƒ (9 nm, 4 µm)
The specs are several times tighter, and
achievable
11
(No Transcript)
12
Pushing visible-light interferometry
Livermore scientists developed the PSDI
or Sommargren Interferometer Single Mirror  Two
beams are launched into a fiber with a time
delay. A pinhole in a mirror creates the test
and reference beams. Complete System One fiber
pinhole at each conjugate.
G. Sommargren, J. Taylor, M. Johnson, D.
Phillion, H. Chapman, A. Barty, et al.
(LLNL) (SPIE 586928,30)
13
High sensitivity to multilayer properties
14
EUV interferometers used at the ALS
15
EUV interferometers used at the ALS  PS/PDI
16
EUV interferometers used at the ALS  LSI
17
the illuminated MET pupil
EUV Light
transmitted light
Kenneth Goldberg, KAGoldberg_at_lbl.gov, SPIE 2005,
590016
18
PS/PDI interferogram
EUV Light
ultra-high accuracy
Kenneth Goldberg, KAGoldberg_at_lbl.gov, SPIE 2005,
590016
19
shearing interferogram
EUV Light
efficient measurement method
Kenneth Goldberg, KAGoldberg_at_lbl.gov, SPIE 2005,
590016
20
A long track record of EUV Interferometry,alignme
nt optimization and imaging at LBNL (since 93)
Berkeley 10x
10xI
10xA
10xB
ETS Set-1
ETS Set-2
MET
10xA
10xB2
10xB2
F2X
2-mirror, 10x Schwarzschild objectivesNA
0.08 ƒ / 6.3
4-mirror, 4x ETS projection opticsNA 0.1 ƒ /
5.0
2-mirror, 5x MET opticNA 0.3 ƒ / 1.67
higher resolution
higher quality
time
21
ETS Projection Optic off-axis, large field
Work sponsored by the EUV LLC
1.1-mmask-to-wafer
M2
M4
M3
M1
22
(No Transcript)
23
(No Transcript)
24
The 0.3-NA Micro-Exposure Tool high resolution
Work sponsored by International SEMATECH
Courtesy of J. Taylor, LLNL
Mirrors Zeiss
MET NA 0.3, ƒ/ 1.67 ? 13.4 nm 5x demag. 200 x
600 µm field capable of 12-nm printing
Coating AssemblyLLNL
25
MET at-wavelength interferometry and alignment
Wavefront measurementduring alignment
MET Micro-Exposure Tool
central field point
astig
0.04 nm
coma
0.06 nm
sph ab
0.04 nm
trifoil
0.14 nm
h-o s.
0.37 nm
RMS
0.55 nm l/24.5
EUV interferometry maps the 3-D field of
view.  Alignment sets astigmatism, coma,
spherical aberration arbitrarily small.
26
Small tolerances necessitate ultra-high accuracy
one nm
wavefront quality of best EUV optic to date
?/24.5 0.55 nm
EUVL ?-tool, required wavefront quality
?/50 0.27 nm
?/135 100 pm
EUV interferometer accuracy _at_ 0.3 NA
?/330 40 pm
EUV interferometer accuracy _at_ 0.1 NA
?/255 53 pm
Bohr radius, a0
27
The keys to achieving ultra-high accuracy
1) Innovative calibration methods (null
tests) 2) New interferogram analysis
techniques for minimizing phase-measurement
errors 3) High-quality reference pinholes
(Nanowriter) We isolate and measure geometric
systematic errorsources so they can be
subtracted.
28
two-pinhole null-test interferogram
system calibration forhigh accuracy
Kenneth Goldberg, KAGoldberg_at_lbl.gov, SPIE 2005,
590016
29
grating null-test interferogram
system calibration forhigh accuracy
Kenneth Goldberg, KAGoldberg_at_lbl.gov, SPIE 2005,
590016
30
Developing state-of-the art pinholes for
sphericalreference-wave accuracy
Pinhole-array diffraction
Nanofabrication (Nanowriter)
TEMPEST-3D Modeling vector E-M field simulations
object pinhole
object pinholes
Intensity
SEM
100 nm
diffraction angle
image pinhole
Intensity
image pinholes
25 nm
TEM
diffraction angle
31
The absence of astigmatism confirms accuracy
39-nm isolated lines
0.1-NA ETS opticlithography at LBNL 13.5 nm
wavelength ? 0.7, partial coherence DOF 0.5
µm EUV-2D resist, 120-nm thick
Coded as 80 nm (11)narrowed by exposurebias
(x1.4)
32
0.3-NA MET Modulation down to 25 nm
45 nm
35 nm
35 nm
25 nm
30 nm
1.8 mm
Rohm and Haas photo-resist R. Brainard, et al.
1.8 mm
33
(No Transcript)
34
Direct visible / EUV comparisons lead to improved
accuracy
35
We also cross-calibrate the different EUV
techniques
visible-light EUV PS/PDI EUV shearing
Inter-comparisons have also improved EUV
testing methods.
36
Conclusions
High-quality EUV optics are available
now largely due to the development of EUV
lithography slope errors lt 1
µrad roughness 12 Å micro-roughness
12 Å Ultra-high accuracy interferometry is
required for fabrication and alignment visible
(LLNL) and EUV (LBNL). We have extended our
EUV measurement techniques to 0.3 NA,
ƒ/1.67  Achieved Wavefront quality of 0.55 nm
(?/24.5).  Demonstrated interferometer accuracy
of 1 Å, and below.
37
Extra slides follow . . .
38
Interferometry across the field of view
image-plane field measurement
nm
Note diameter magnitude
Initial measurements showed a large spherical
aberration 0.80.9 nm  Field measurements are
made at 9(x,y) ? 3(z) 27 points, 135
interferograms, 3 hours.
39
Using interferometry to optimize the MET
alignment
image-plane field measurement
nm
Note diameter magnitude
Reduced the aberration magnitude to 0.55 nm
?/24.5  Set astig., coma, and sph. ab. to ?/225
?/340
40
Different kinds of interferometry are used
Visible-light Sommargren Interferometer
(LLNL) EUV Knife-edge (Foucault)
testing  Lateral Shearing Interferometry
(LSI) - cross-grating technique  Phase-shifting
point-diffraction interferometry - ultra-high
accuracy - invented at CXRO  Hartmann test -
best for low-NA
41
astigmatism 111 pm coma 47 pm spherical 297
pm trifoil 292 pm ?37 RMS 703 pm
EUV deviation from a perfect, spherical
wavefront ? 13.4 nm
Kenneth Goldberg, KAGoldberg_at_lbl.gov, SPIE 2005,
590016